[NEW] Support Video and Audio calling in Livechat

Co-authored-by: Murtaza Patrawala <34130764+murtaza98@users.noreply.github.com>

[NEW] Add support to notify call declined and fix call status API to update message by passign callId

Co-authored-by: Renato Becker <renato.augusto.becker@gmail.com>

* Release 1.0.0-alpha.29

* Set up Livechat connections on server side.

* Update connect method.

* Read token from credentials.

* Add new method to fetch Livechat messages.

* Replace param interface.

* Add agentId parameter when getting a new Livechat room.

* Add new Livechat Interface.

* Fix Interface structure.

We should use fat arrows instead of E5 functions because of binding.
I'm applying new JS SDK into React Native app, that implies binding more than usual.
For example: `subscribeRoom` works perfectly in node, but it raises the following error on RN.
<img width="350" src="https://user-images.githubusercontent.com/804994/52142654-61acfc80-2640-11e9-8d25-a5a5f6faf86f.png" />
This happens because `this.subscribe` doesn't exist on `this` scope.

Depends of: https://github.com/RocketChat/Rocket.Chat/pull/13073 and https://github.com/RocketChat/Rocket.Chat/pull/12982.

https://github.com/RocketChat/Rocket.Chat.Livechat/projects/2#card-16166223

* Added function to upload a file in livechat

* Fix indentation.

- [x] Change some functions to make it return the response returned by endpoint instead the unresolved promise.

- [x]  Change some functions signatures, removed the params which contained the livechat token, change it to use the `credentials.token` available on the SDK. Affected functions below:
```
async config (params?: ILivechatTokenAPI)
visitor (params: ILivechatTokenAPI)
```
https://github.com/RocketChat/Rocket.Chat.Livechat/projects/2#card-16169691

[FIX] paho mqtt repository